A tank reaches full maturity at around 6 months. So, I'd be patient about adding the more expensive and more sensitive fish like the rams, gouramis and angelfish. And what would be the reason for adding the BN plecos before they had some algae to munch. Let the algae build up a little first so that they will have some "natural" food when they are added... Maybe a month or so from now. I might think about adding the gouramis the month after that, then the rams and finally the angels. But, as mentioned... breeding angels can be a bit testy.
The most valuable lesson taught to me about this hobby was to "Look at the science." And when I approach what your saying from that angel I can't help but disagree in an aquatic sense (not personal.) This notion of "sensitive" fish when you break it down is actually fish which are least tolerant to ammonia, nitrite, and the higher levels of nitrate. If none of the aforementioned are present what is to stop someone adding their stock? Secondly, a tank reaching full maturity in 6 months has never made much sense to me. I mean, sure you might get diatoms algae on the glass for 6 months and perhaps longer but again, what is the science behind this tank maturity thing?
My theory behind these commonly accepted rules is this...
Too many people don't "fully" cycle their filter (cycling to a lower ppm like the original post) and then add their full stock. Inevitably they get spikes of ammonia or nitrite. Sometimes these spikes are mere traces but traces which are sustained (perhaps ammonia @ 0.25ppm) and as a result the species in their stock which is most susceptible die.
The maturity thing also (to me) seems quite baseless. And I say that because the bac colony after you cycle is at it's strongest. And will adjust in numbers according to the A & N available. If you cycle to the point where 5ppm of ammonia (and the resulting nitrite) is consistently consumed within 12 hours and then add a school of tetras and say a couple of other fish while waiting for the tank to "mature" all your doing, scientifically, is reducing the size of your bacs colony, only to then build up the colony slowly over time by adding a fish here and there. Where as if you stock fully to begin with, the bacs colony will adjust in size accordingly. Making the bacs you then lose of zero consequence to your fish.
I remember when I first finished my cycle and wanted neon tetras and everyone was telling me "No you've got to wait" or "Neon tetras are just too sensitive" and inevitably "You must wait for your tank to mature?" It was around that time, no in fact it was exactly that time where someone from this very forum told me to identify the science. Green neons were the first fish I added to my aquarium on stock day without issue.
Again though, I would love to read or see the science behind the "tank maturity" and "sensitive fish." While I'm confident in the science of this hobby there is so much to learn so if someone could point out to me the science behind these commonly carted rules, I'm more than willing and would love to learn more about them.
@kashifg I wouldn't add anything to the tank until 5ppm of ammonia is consumed within 12 hours consistently for 7 days.
This is a big tank so will need a decent amount of fish to keep up after the fishless cycle. If you just add a few fish - eg one school - each time you add only a few fish the bacteria will die off as there will not be enough ammonia and nitrate to feed the full colony so each time you add more fish you will bump the cycle somewhat. 
